Extraocular Phototransduction: more than meets the eye? (part 2)

We recently drew attention to the 1998 discovery at Cornell regarding the possibility of tweaking one’s cicadian rhythms by shining a bright light at the back of one’s knees. But continuing research into extraocular (outside the eye) light stimuli has turned to the possibility of a more direct route. Why not shine a light directly into one’s brain? Fortunately, there’s no need to resort to trepanning, because (at least) two convenient pathways already exist for brain illumination. Namely the ear canals. A research team from the University of Oulu, Finland (“Creating Innovation for the Future”) tested volunteers while they underwent blood oxygen level dependent (BOLD) functional magnetic resonance imaging scanning (fMRI) as a bright light was delivered via their external ear canal :

“Light was produced by two 3 W LEDs (main light spectrum peak at blue light 465 nm and a secondary peak at 550 nm) and delivered via 5 meters long polycarbonate colourless fiber optic light guides connected to ear-plugs in the subject’s ears while inside the scanner.”

Findings from the study :

“…suggest that the brain possesses photosensitive properties, which will have interesting implications for the modulation of brain function and understanding the basic physiology of the brain.”

But, the authors add :

“The mechanism for the phototransduction of the brain tissue remains to be discovered and we are currently investigating it in more depth.”

[1] “ Some of the authors have conflicts of interests with a company, Valkee Ltd., that develops and sells devices for bright light stimulation via ear-canal. Authors’ connections with Valkee Ltd. are: Nissilä and Aunio are company founders. Nissilä, Aunio, Takala and Timonen are share-holders (varying from major to minor). Nissilä, Aunio and live-in partner of Starck are employed by Valkee Ltd. Valkee Ltd. did not have a role in the decision to submit the paper for publication.”